Charge density waves (CDW) and superconductivity (SC) are observed in a variety of materials such as layered transition-metal dichalcogenides, high-temperature cuprates, organic compounds, and other novel superconductors. The question as to whether CDW cooperate or compete with SC in those materials is under hot debate. The work presented in this seminar has been motivated by two recent ARPES experiments of NbSe_2, one claiming the observation of cooperation [1] and the other claiming competition [2] of CDW and SC. In terms of the Bogoliubov-de Gennes formalism of superconductivity, we study the possible origin of CDW and its interplay with SC within a minimal tight-binding model.
[1] Kiss et al., Nature Physics 3 (2007) 720
[2] Borisenko et al., Phys. Rev. Lett. 102 (2009) 166402